LATITUDE.

I have endeavoured to collect in one point of view the whole of the
physical phenomena of that part of the New Continent comprised
within the limits of the torrid zone from the level of the Pacific
to the highest summit of the Andes; namely, the vegetation, the
animals, the geological relations, the cultivation of the soil, the
temperature of the air, the limit of perpetual snow, the chemical
constitution of the atmosphere, its electrical intensity, its
barometrical pressure, the decrement of gravitation, the intensity
of the azure colour of the sky, the diminution of light during its
passage through the successive strata of the air, the horizontal
refractions, and the heat of boiling water at different heights.
Fourteen scales, disposed side by side with a profile of the Andes,
indicate the modifications to which these phenomena are subject
from the influence of the elevation of the soil above the level of
the sea. Each group of plants is placed at the height which nature
has assigned to it, and we may follow the prodigious variety of
their forms from the region of the palms and arborescent ferns to
those of the johannesia (chuquiraga, Juss.), the gramineous plants,
and lichens. These regions form the natural divisions of the
vegetable empire; and as perpetual snow is found in each climate at
a determinate height, so, in like manner, the febrifuge species of
the quinquina (cinchona) have their fixed limits, which I have
marked in the botanical chart belonging to this essay.

1.I.5. OBSERVATIONS ON ZOOLOGY AND COMPARATIVE ANATOMY.

I have comprised in this work the history of the condor;
experiments on the electrical action of the gymnotus; a treatise on